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Paul Mangum and Ellen Peffley

(Allium cepa × A. fistulosum) × A. cepa breeding lines have been established to the fourth generation. The aim is to develop an A. cepa-like bulbing onion carrying A. fistulosum genes. Seven populations were characterized for morphological traits and three isozyme markers. Each bulb from the populations was characterized for maturity, soluble solids content, bulb shape, and bulb color. All the populations produced A. cepa-like bulbs. Significant variation was observed within each population for each morphological trait. All the bulbs were screened for the presence of A. cepa and A. fistulosum alleles of alcohol dehydrogenase (Adh-1), esterase (Est), and phosphoglucoisomerase (Pgi-1). Allium cepa Adh-1, Est, and Pgi-1 alleles were observed in all the populations. One population, 951026-8, contained plants heterozygous for A. cepa and A. fistulosum Pgi-1 alleles. Recovery of these fourth generation Allium backcross plants demonstrates introgression of the A. fistulosum genome into an A. cepa-like bulbing onion.

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Ryan J. Hayes*, Ed Ryder, and Bert Robinson

Big vein (BV) disease of lettuce is caused by soil borne fungal vectored viruses, and reduces marketability through head deformation. Tolerant cultivars reduce BV frequency, but no resistant cultivars exist. L. virosa L. is highly resistance. The objectives were to 1) determine if L. virosa P.I.s exhibit variation for resistance, and 2) determine if resistance is transferable to lettuce. Seedlings were inoculated with root macerate of BV infected plants, transplanted to BV infested soil, and greenhouse grown for 3 months. Twelve plants in each of 1,2, or 3 reps of Great Lakes 65 (GL65-susceptible), Pavane (Pav-tolerant), L. virosa (11 accessions), and BC1 F2 through F5 families of lettuce cultivars x L. virosa accession IVT280 were tested. The percentage of BV afflicted plants was recorded. In hybrid families, BV free plants from tolerant families were selected and advanced. No BV was found in L. virosa. Variation for tolerance was observed in BC1 F2 and F3 families; 33% had greater tolerance than Pav (17% afflicted). Additional tests identified 11 BC1 F3 families (14%) with greater tolerance than Pav (42% afflicted). Subsequent BC1 F4 and F5 generations however, were more susceptible than Pav. Lactuca virosa is highly resistant, but resistance did not transfer to hybrid progeny. Variation for tolerance was observed in BC1 F2 and F3 families, but later generations were susceptible. Interactions or linkage of genes for developmental processes and BV resistance may hinder introgression. Introgression will continue using congruity backcrossing and a greater diversity of L. virosa.

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Peter M. Hanson, Dario Bernacchi, Sylvia Green, Steven D. Tanksley, Venkataramappa Muniyappa, Attiganal S. Padmaja, Huei-mei Chen, George Kuo, Denise Fang, and Jen-tzu Chen

Tomato yellow leaf curl virus (TYLCV), a heterogeneous complex of whitefly-vectored geminiviruses, is a serious production constraint of tomato (Lycopersicon esculentum Mill.) in Asia, the Middle East, and the Americas. In this study we report on mapping of a DNA fragment introgressed into cultivated tomato presumably from the wild species L. hirsutum Humb. and Bonpl. and found to be associated with TYLCV resistance. To locate introgressions of wild tomato alleles in TYLCV-resistant tomato line H24, its DNA was digested with six restriction enzymes and probed with 90 RFLP markers evenly spaced throughout the genome. This polymorphism survey revealed the presence of one wild tomato introgression each on chromosomes 8 and 11. Plants of a F2 cross between H24 and a susceptible tomato line were probed with randomly amplified polymorphic DNA (RFLP) markers linked to the targeted regions and F3 families were developed by self-pollination of F2 plants that carried none, one, or both introgressions in either homozygous or heterozygous states. Plants of F3 families, parents, and control tomato line Ty52 (homozygous for the Ty-1 allele for TYLCV tolerance) were exposed to viruliferous whiteflies (Bemisia tabaci Gennadius) in greenhouses at the Asian Vegetable Research and Development Center, Taiwan, and the University of Agricultural Sciences, Bangalore, India. Results indicated that F3 families homozygous for the introgression on chromosome 11 were resistant to TYLCV at both locations. Additional probing showed that the chromosome 11 introgression spanned markers TG36 to TG393, covering a distance of at least 14.6 centimorgans. This is the first report of TYLCV resistance in tomato mapped to chromosome 11.

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Samuel F. Hutton, Yuanfu Ji, and John W. Scott

to Ty-1 ( Verlaan et al., 2013 ). Linkage drag in the form of increased foliar disease and reduced yield has also been a problem in lines possessing Ty-3 . Fla. 8923 is a large-fruited breeding line with a much reduced introgression that is free of

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Gorka Perpiñá, Jaime Cebolla-Cornejo, Cristina Esteras, Antonio J. Monforte, and Belén Picó

‘MAK-10’ is a new breeding line derived from a collection of introgression lines (ILs) developed from the cross between the Japanese cultivar ‘Ginsen makuwa’ PI 420176 ( Cucumis melo Group Makuwa) and the French cantaloupe variety ‘Vedrantais’ ( C

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Ryan J. Hayes and Edward J. Ryder

resistance has not been introgressed into lettuce cultivars. Although L. sativa and L. virosa are both 2n = 2x = 18, introgression of L. virosa genes is complicated by extreme sterility in the hybrid progeny. L. virosa is evolutionarily divergent from

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Francisco Javier Palomares-Rius, Ana Garcés-Claver, María Belén Picó, Cristina Esteras, Fernando Juan Yuste-Lisbona, and María Luisa Gómez-Guillamón

’ ( C. melo ssp. melo ). Origin The melon line ‘Carmen’ was obtained by introgression of powdery mildew, CYSDV and A. gossypii resistances of TGR-1551 into the genetic background of the Spanish cultivar Bola de oro (Yellow Canary type). Five

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Paul M. Lyrene

× highbush cultivar crosses, indicating that V. stamineum introgression had not reduced berry size. Fig. 6. Internal berry color of freshly sliced mature berries of tetraploid selection FL 15-669 (a highbush cultivar × tetraploid V. stamineum F 1 hybrid

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Richard E. Durham and Schuyler S. Korban

DNA was extracted from leaves of various Malus genotypes and used to screen synthetic decamer oligonucleotide primers. Samples from the following two groups were bulked: 1) seven scab-susceptible apple cultivars, and 2) 15 scab-resistant apple genotypes derived by introgressive hybridization from the previous group of cultivars. A third sample consisted of DNA extracted from Malus floribunda Sieb. clone 821, the original source of apple scab resistance for all genotypes in the second group. A total of 59 primers from kits A, L, and R (Operon Technologies) were screened. Amplified fragments were obtained for 93% of the primers tested, while random amplified polymorphic DNA (RAPD) fragments were detected among samples for 76% of the primers. One primer, A15, amplified a unique band in both M. floribunda clone 821 and the bulked scab-resistant sample. This RAPD marker, designated OA15900, identifies an amplified, introgressed fragment that likely corresponds to a region of the genome that may serve as a modifier for the scab resistance gene block V, derived from M. floribunda clone 821.

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M.J. Havey and O.H. Bark

Open-pollinated (OP) onion (Allium cepa L.) cultivars are primarily in normal (N) fertile cytoplasm; however, specific cultivars possess both N and sterile (S) cytoplasm or are exclusively in S cytoplasm. It is unclear whether the presence of S cytoplasm in OP cultivars is due to ancient or recent introduction or both. Restriction-enzyme analysis of the chloroplast DNA established that S cytoplasm has been introgressed into OP onion cultivars since its discovery in 1925. `Valencia Grano' (released in 1927), `New Mexico Early Grano' (1931), `Texas Early Grano (TEG) 502' (1947), and `Temprana' (1979) are in N cytoplasm; S cytoplasm was introduced into the population `TEG 502 PRR', and subsequent selections (`NuMex BR1' and `NuMex Sunlite') are in S cytoplasm. The inbred `TEG 951 C' and `Texas Grano 1015Y' possess a mixture of N and S cytoplasm and, because these two onions originated from self-pollinations of single plants, bulb or seed mixtures or both must have occurred.